As people's demand for higher communication bandwidth continues to grow, Fiber-to-the-x (FTTx) techniques have seen rapid developments, and FTTx techniques spearheaded by Passive Optical Networks (PONs) have been put to an array of applications.
The PON typically includes an optical line terminal (OLT) mounted at a centralized control station, and optical network units (ONUs) correspondingly mounted at various user sites. The ONU is provided with a laser which emits light, as well as a laser driver which drives the laser to emit the light. Since the OLT must be coupled to a plurality of ONUs during an interfacing transaction between the OLT and the ONU, each ONU is allocated with a specific operation period. When in non-operation mode, an ONU does not emit light. If light is nonetheless emitted, the ONU will be found to be in a rogue state, a situation that requires the laser driver to cut-off.
In prior arts, one way to control the cut-off of the laser driver is software control, which is typically performed at program level, with a cut-off command being communicated via a bus, i.e. an inter-integrated circuit (I2C), to the laser driver so that the laser driver may carry out the cut-off process.